Manufacture of alkyl phosphates



Patented Dec. 1, 1936 UNITED STATES MANUFACTURE OF ALKYL PHOSPHATES Vladimir Ipatieff, Chicago, 111., assignor to Universal Oil Products Company, Chicago, 111., a corporation oi Delaware No Drawing. Application April 30, 1932, Serial No. 608,572

2' Claims.

This invention relates to the production of esters, and more particularly to the manufacture of esters of certain mineral acids.

In a more specific sense the invention is con- 5 'cernedwith an improved process for the manufacture of alkyl esters of phosphoric acid by direct combination of olefins therewith under special conditions of operation which enable the reactions leading to ester formation to proceed with great rapidity and produce high yields of desired products.

In one specific embodiment the invention comprises treatment of olefins with sulfuric and phosphoric acid under superatmospheric pressure.

The commonly used methods of producing esters of mineral acids are described below: The first and perhaps simplest method consists in directly reacting an alcohol and a mineral acid, an equation expressing a, reaction of this character being as follows:

2 CnHsOH H2804 (:119:30; +2Hz0 Ethyl alcohol Sulfuric acid Diethyl sulfate It will be seen that the completion of the above reaction depends upon the abstraction of water which is usually accomplished by using an excess of strong sulfuric acid in the reaction mixture so that the final yield of product is considerably less than that theoretically possible with a given amount of the acid.

A second method which can be utilized for ester production consists in reacting alkyl halides, preferably the iodides, With silver salts such as, for example, silver nitrate as shown by the following equation:

CzHsI AgNOa ozHaNOR AgI 0 Ethyl iodide Sllvernitrate Ethyl nitrate Silveriodide 4 This type of reaction involving as it does the use of relatively large quantities of silver'compounds is impractical in the case of commercial production from the standpoint of cost and also frequently diificult to manipulate to produce esters of a high grade of purity.

A third possible method involves the interaction of alcohols or alcoholates with acid chlorides as typified by the following equation:

2CH OH $02012 Ethyl alcohol Sulfuryl chloride oimnsoi 21101 Diethyl sulfate Hydrochloric acid The commercial application of this method also involves serious operating difiiculties in commercial practice and is not used extensively other than on a laboratory scale.

The foregoing methods are generally of an involved and tedious character comprising the use of relatively expensive materials and on this account attempts have been made from time to time to devise simpler and less expensive processes. For example, numerous experimenters have sought to produce esters by the direct combination of olefins with such acidsas sulfuric and phosphoric acid, but these processes as a rule have been commercially unprofitable due to the low absorption rate under conditions necessary to prevent polymerization of the olefins.

I have determined that-by the use of superatmospheric pressures that the rate of absorption of olefins in acids is materially increased at any given temperature and that the replaceable hydrogen atoms in polybasic acids may be successively replaced by alkyl groups to form welldefined compounds with substantially no formation of polymerized products. To exemplify the results obtainable by the use of pressure according to the process of the invention the following test data is submitted.

In the experiments which furnished this data the phosphoric acid used consisted of 95% by weight of orthophosphoric acid (HaPOr), the remainder being water:

Table .Cc. Init. press. Final press. Gm. ethyl- Inc. in HsPOi Catalyst Amt. 2? 25 of ethylene of ethylene one abwt. of 50 used per sq. in. per sq. in. sorbed soln Percent 1 70 96% H1804 7. 5 cc. 375 12 903 452 21 17. 5 2 62 100% H1804 4. 0 cc. 380 21 889 677 17 15. 9 3 60 CuiO 3 g. 390 13 875 664 23 22. 2

The rate of absorption was found to be further accelerated by the use of small amounts of catalytic material, especially with phosphoric acid when using such catalysts as sulfuric acid and cuprous oxide as shown in the table. It was further found necessary to use somewhat elevated temperatures in addition to superatmospheric pressures to attain higher absorption rates. The principal product formed was the mono ester corresponding to the substitution of one hydrogen atom by the ethyl group. Again substantially no polymerization was noted.

The process is specially applicable to the formation of esters from gas mixtures containing high percentages of olefinic hydrocarbons 'such as the gas mixtures produced in cracking plants which frequently contain as high as 20% of oleflns such as ethylene, propylene and the various butylenes and isobutylenes. By introducing such gas mixtures under pressure into treaters containing sulfuric acid, phosphoric acid, and the like, under proper temperature conditions, satisfactory yields of mixed esters are obtainable with a. minimum of polymerization, the esters thus formed being utilizable in the arts as such or serving as base materials for the manufacture of secondary alcohols, saturated hydrocarbons and other compounds. Thus. alcohol mixtures may be produced by hydrolysis of the esters and saturated hydrocarbons may be formed by treatment with metals. Within certain limits the process is applicable to mixtures containing oleflns, such as cracked products. The temperatures of treatment will vary, dependent upon the degree of superatmospheric pressure used.

The foregoing description 'of the process of the invention'and the experimental data given to show its advantages are neither to be construed in the light of imposing undue limitations upon the broad scope of the invention as they have been given for illustrative purposes only.

I claim as my invention:

1. A process for producing phosphoric acid esters which comprises reacting phosphoric acid a gaseous oleflnic hydrocarbon in the presence of sulphuric acid as a catalyst and under superatmospheric pressure. V

2. A process for producing phosphoric acid esters which comprises reacting phosphoric acid with an olefinic hydrocarbon in the presence of sulphuric acid as a catalyst and under superatmospheric pressure.

VLADIMIR. IPA'I'IEFF. 

